VMS Help CMS, CREATE, ELEMENT, Qualifiers, /RESERVE  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    Controls whether the new element is to be reserved after it is
    created. When you specify /RESERVE, CMS does not delete the file
    used to create the element. Generation 1 of the newly created
    element is automatically reserved.

    If you omit both the /RESERVE and the /KEEP qualifiers, CMS
    deletes all versions of the file used to create the element.